Underground conduits are widely used for the transmission of fluids and gases, such as in pipelines and the like, as well as for carrying wires and cables for the transmission of electrical power and electrical communications signals. While the installation of such conduits is time-consuming and costly for locations where the earth can be excavated from the surface, the routing of such conduits becomes more difficult where the surface excavation cannot be done due to the presence of surface obstacles through which the excavation cannot easily proceed. Such surface obstacles include highways and railroads where the installation of a crossing conduit would require the shutdown of traffic during the excavation and installation. Such surface obstacles also include rivers, which present extremely difficult problems for installing a crossing conduit due to their size and difficulty of excavation thereunder.
Prior methods for the installation of conduit have included the use of directional drilling for the formation of an enrouted underground arcuate path extending between two surface locations and under the surface obstacle with the conduit installed along the drilled path. A conventional and useful method for installing such underground conduits is disclosed in U.S. Pat. No. 4,679,637, issued Jul. 14, 1987, assigned to Cherrington Corporation, and U.S. Pat. No. 4,784,230, issued Nov. 15, 1988, assigned to Cherrington Corporation, both of which are incorporated by reference herein.
Several shortcomings of the prior methods are discussed in connection with U. S. application Ser. No. 557,992, filed Jul. 26, 1990, entitled "Improved Method and Apparatus for Enlarging an Underground Path", to Martin Cherrington and assigned to Cherrington Corporation, which is also incorporated by reference herein. A major concern in forming an underground conduit in a near horizontal position is the removal of cuttings resulting from the reaming operation. These cuttings may inhibit the pre-reaming and reaming operations and further inhibit the installation of the pipeline. It is believed that the cuttings, many of which are heavier than the fluid transporting them, will settle towards the bottom of the underground hole and then build up into a circumferential packed mass, especially when the rate of reaming is poor.
One application of horizontal conduits is for removing fluids and gases from a subterranean area. For example, a horizontal well could be drilled to reach an aquifer which would otherwise be unreachable because of a man-made or natural structure above the aquifer. Another application would be the removal of hazardous wastes which have leached into the soil, for example, from a oil tank above the subterranean area. A third application would be the infusion of gases or liquids into a subterranean area from a above-ground station.
In these applications, it is desirable to have a filtering medium, such as gravel, surrounding a slotted, or otherwise porous, pipe. Heretofore, centering a slotted pipe within a horizontal hole and surrounding the pipe with the filtering medium has been problematic. Prior art methods, such as filling the horizontal hole with a gravel and water mix and removing the water through the slotted pipe have proven ineffective in wells having a hole angle of approximately 45.degree.-50.degree. from the vertical. If the slotted pipe is not sufficiently surrounded with the filtering medium, materials from the horizontal hole will clog the slotted pipe and may foul the liquid or gas being removed. Furthermore, the cuttings remain in the hole, the filtering medium may become contaminated, thereby reducing its effectiveness.
Therefore, a need has arisen for a effective method and apparatus for installing a horizontal porous pipe surrounded by a filtering medium.